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.\" $Id: elf_cntl.3 3953 2022-03-12 09:57:05Z jkoshy $
.\"
.Dd August 9, 2006
.Dt ELF_CNTL 3
.Os
.Sh NAME
.Nm elf_cntl
.Nd control an elf file descriptor
.Sh LIBRARY
.Lb libelf
.Sh SYNOPSIS
.In libelf.h
.Ft int
.Fn elf_cntl "Elf *elf" "Elf_Cmd cmd"
.Sh DESCRIPTION
Function
.Fn elf_cntl
controls the ELF library's subsequent use of the file descriptor
used to create ELF descriptor
.Fa elf .
.Pp
Argument
.Fa cmd
informs the library of the action to be taken:
.Bl -tag -width "ELF_C_FDDONE"
.It Dv ELF_C_FDDONE
This value instructs the ELF library not to perform any further
I/O on the file descriptor associated with argument
.Fa elf .
For ELF descriptors opened with mode
.Dv ELF_C_WRITE
or
.Dv ELF_C_RDWR
subsequent
.Fn elf_update
operations on the descriptor will fail.
.It Dv ELF_C_FDREAD
This value instructs the ELF library to read in all necessary
data associated with ELF descriptor
.Fa elf
into memory so that the underlying file descriptor can be
safely closed with command
.Dv ELF_C_FDDONE .
.El
.Pp
Argument
.Fa elf
must be an ELF descriptor associated with a file system object
(e.g., an
.Xr ar 1
archive, an ELF file, or other data file).
.Sh IMPLEMENTATION NOTES
Due to use of
.Xr mmap 2
internally, this function is a no-op for ELF objects opened in
.Dv ELF_C_READ
mode.
.Sh RETURN VALUES
Function
.Fn elf_cntl
returns 0 on success, or -1 if an error was detected.
.Sh ERRORS
.Bl -tag -width "[ELF_E_RESOURCE]"
.It Bq Er ELF_E_ARCHIVE
Argument
.Fa elf
is a descriptor for an archive member.
.It Bq Er ELF_E_ARGUMENT
Argument
.Fa elf
was
.Dv NULL .
.It Bq Er ELF_E_ARGUMENT
Argument
.Fa cmd
was not recognized.
.It Bq Er ELF_E_MODE
An
.Dv ELF_C_FDREAD
operation was requested on an ELF descriptor opened
for writing.
.El
.Sh SEE ALSO
.Xr elf 3 ,
.Xr elf_begin 3 ,
.Xr elf_end 3 ,
.Xr elf_next 3 ,
.Xr elf_update 3 ,
.Xr gelf 3
